The invention relates generally to hand tools and more particularly to tools for removing retaining snap rings from cylindrical shafts.
Retaining snap rings are widely used in mechanical apparatus for removably connecting springs, collars, and other parts to cylindrical shafts. Typically, the shaft is provided with an annular groove for receiving a snap ring to hold such other part in a desired longitudinal position along the shaft. In general, the snap rings comprise a ring of highly resilient metal, such as spring-quality steel. Such rings have a split or gap in one side which is smaller than the diameter of the shaft at the base of the annular groove. The gap in the snap ring must be opened sufficiently against the spring tension of the ring to pass over the diameter of the shaft when mounting or removing the ring. Snap rings come in a wide variety of shapes and sizes, but typically have a generally rounded outer surface. Ordinarily, the inner diameter of snap rings is slightly larger than the diameter of the shaft within the annular groove. Thus, such rings can rotate fairly easily around the shaft. These features of the rings make their removal and installation extremely difficult.
A number of snap ring removal and installation tools have been proposed. One type of tool is disclosed in U.S. Pats. to Epstein, No. 3,762,019, and Kulba et al, No. 3,990,137. These tools comprise pliers whose jaws carry a pair of parallel pins which are inserted into the gap between the ends of a snap ring and are moved away from one another to open the snap ring for removal by squeezing the handles of the pliers together. However, the end faces of the snap ring, at opposite ends of the gap, must be close together, substantially parallel, and inwardly opposed for the pins of the pliers to obtain an adequate grip. Otherwise, the pins tend to slip from the gap as they are being spread apart against the spring-tension of the snap ring. Since many types of snap rings are made with radial non-parallel end faces which are spaced apart to ease installation of the ring on a cylindrical shaft, it is preferable to have a tool which does not require parallel end faces to work.
In response to this need, two other pliers-type tools have been proposed in U.S. Pats. to Stilwell, No. 2,737,837, and Nakamoto, No. 4,135,284. The tools proposed in such patents each include means for holding a snap ring rigidly in the tool as its ends are spread apart for removal or installation. However, snap rings are often positioned in machinery in a location such that the tool cannot be positioned around the snap ring. In addition, such tools require easy access to the snap ring from a radial side of the shaft on which the ring is mounted.
Another group of tools do not rely upon engagement between the end faces of the snap ring to open the ring for removal or installation. These tools are described in U.S. Pats. to Wurzel, No. 2,835,028; Tuller, No. 3,173,197; Carpenter, No. 3,340,592; Hosbach, No. 3,470,600; and Erdmann, No. 3,785,037. These tools have means for engaging two outer sides of a snap ring on laterally opposite sides of the gap for urging the snap ring in a direction normal to the axis of the shaft to install or remove the ring. However, the tools in this last group all suffer from the same disadvantage that the second group of tools suffered from; namely, requiring access to the snap ring in a radial direction from the axis of the shaft.
Although many snap rings can be readily installed or removed using such tools, many other snap rings are inaccessible from such direction. For example, in removing snap rings from the armature shaft to disassemble certain types of automotive starters, such as those made by Ford Motors since 1960, access can be obtained to the snap ring only along a path that is generally parallel to the axis of the shaft. None of the above-referenced tools can be used for removing or installing snap rings on such shafts. Therefore, the entire starter must be disassembled to replace the starter drive. This requires two to three minutes. Since a large automotive electric shop may rebuild hundreds of starters a week, the amount of time spent disassembling and reassembling starters becomes very great.
Accordingly, there remains a need for a snap ring removal tool which can be used in situations in which the only access to the snap ring to be removed is substantially parallel to the axis of the shaft. There also remains a need for a tool to aid in installing snap rings in such environment.